The first reliable report on the 1H-imidazo[4,5-c]quinoline ring system, Backman et al., J. Org. Chem. 15, 1278–1284 (1950) describes the synthesis of 1-(6-methoxy-8-quinolinyl)-2-methyl-1H-imidazo[4,5-c]quinoline for possible use as an antimalarial agent. Subsequently, syntheses of various substituted 1H-imidazo[4,5-c]quinolines have been reported. For example, Jain et al., J. Med. Chem. 11, pp. 87–92 (1968), has synthesized the compound 1-[2-(4-piperidyl)ethyl]-1H-imidazo[4,5-c]quinoline as a possible anticonvulsant and cardiovascular agent. Also, Baranov et al., Chem. Abs. 85, 94362 (1976), and Berenyi et al., J. Heterocyclic Chem. 18, 1537–1540 (1981), have reported certain 2-oxoimidazo[4,5-c]quinolines.
Following the above report, 1H-imidazo[4,5-c]quinolin-4-amines and 1- and 2-substituted derivatives thereof were found to be useful as antiviral agents, bronchodilators and immunomodulators. These are described in U.S. Pat. Nos. 4,689,338; 4,698,348; 4,929,624; 5,037,986; 5,266,675; 5,268,376; 5,346,905; 5,389,640; 5,605,899; 5,352,784; 5,446,153; and 5,482,936. Shen et al., U.S. Pat. Nos. 4,038,396 and 4,131,677, describe certain oxazolo-and thiazolopyridines as having antiinflammatory, analgesic, and antipyretic properties.